Anyone have experience using bonded cellular connections? If I understand correctly, I need to buy separate LTE modems, each with their own service plan, in order for it to work, right? Obviously, it will depend on the specific equipment I'm using.

The Teradek solution is the most cost-effective, however, we use LiveU. It's very reliable, used globally by major broadcasters such as CNN (US), NBC (US), NRK (Norway), ABC (Australian Broadcasting), Sinclair (US), Raycom (US), Meredith (US), Cox (US), Fox (US), and others. Depending on the field encoder you use, you can get them with sim cards built-in already or use USB cellular modems. If you purchase their monthly service, you can have multiple cellular carrier sim cards/USB modems and just pay LiveU for whatever bandwidth you use on the various carriers (as opposed to purchasing modems/service from carriers separately and then having multiple bills each month.) Their LiveU central service is also very intuitive, and since its web-based, it can be run from PC's or Macs. And since it is fairly common with stringers for the various news broadcasters in the US, its relatively easy to find owner/operators in all the major markets in the US (if that is something that would be of value to you.)

You can also use livestream studio to livestream.com on a laptop with a few LTE cards and (this is the big advantage) every other kind of internet connection like lan or wlan.With a BM Mini Recorder over Thunderbolt you get your signal into the computer.You even have the possibility to get inserts, play videos and record, and you can see directly what´s happening and you don´t need a receiving server since livestream.com can do that.